JPS6236579A - Optical current and magnetic field measuring apparatus - Google Patents

Abstract

PURPOSE:To enable highly sensitive construction of the apparatus even in the use of a polarization beam splitter with the same shape as polarizer and analyzer, by building up a part or the hole of a light transmitting part of the magnetooptical element of a material having a natural optical rotary power. CONSTITUTION:A polarizer 3a is arranged between the output terminal of an optical fiber 2 and an incident surface 9d, and an analyzer 3b between an emission surface 9e and the input terminal of an optical fiber 7. A magnetic field 5 is applied so as to pass entirely through a magnetooptical element 9. Moreover, the magnetic field 5-wise length L of the magnetooptical element 9 is adjusted to the rage in which the polarization surface of the linearly polarized light incident into the magnetooptical element 9 turns by 45 deg. with a natural optical rotary power when the light emits from the magnetooptical element 9. As a result, the polarization surface of the polarizer and the analyzer can be square or parallel, thereby permitting a high sensitivity even in the use of a polarization beam splitter with the same shape is used.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical current/magnetic field measuring device that measures the magnitude of current or magnetic field by utilizing the magneto-optical effect, particularly the Faraday effect.

[Conventional technology]

Figure 3 shows a conventional optical applied current/magnetic field measurement device. Figure 1 and Figure 2 show 1 and 2, where 1 is the light source, 2 is the original fiber that propagates the light from the light source 1, and 3 is the linearly polarized light emitted from the original fiber 2. 4 is a magneto-optical element having a magneto-optic effect, such as a Faraday effect.

5 is the applied magnetic field to be measured % 6 is an analyzer placed opposite to the polarizer 3 via the magneto-optical element 4, T is the original fiber into which the light emitted from the analyzer 6 is incident and propagated, 8 is the original fiber This is an optical receiver that receives the light emitted from the fiber T and converts it into an electrical signal amount.

Figure 4 shows polarizer 3, magneto-optical element 4° analyzer 6 in Figure 3.
This is a simple illustration of the component parts shown in the figure, and shows that the polarizer 3 and analyzer 6 have different shapes.1 Both are composed of polarizing beam splitters made of laminated thin films. ing.

Next, the operation will be explained.

The light emitted from the light source 1 is passed through the original fiber 2 to the polarizer 3
and is converted into linearly polarized light by the polarizer 3. When this linearly polarized light passes through the magneto-optical element 4 to which a magnetic field 5 as shown in FIG. Rotate.

Letting this rotation angle be θ, the rotation angle θ becomes θ=ve−L−H. Here, Ve is the Guelde constant of the magneto-optical element 4, and the larger this value is, the larger the rotation angle θ becomes. L is the length of the optical path in the magneto-optical element 4 in the direction of the magnetic field 5;
H is the applied magnetic field 5.

The element emitted from the magneto-optical element 4 is incident on an analyzer 6, and the analyzer 6 extracts an element with an intensity corresponding to the rotation angle θ. The polarization plane of the analyzer 6 is normally arranged to form an angle of 45 with the polarization plane of the polarizer 3 in order to maximize detection sensitivity.

When using the polarizing beam splitter as the analyzer 6,
In order to form the above-mentioned angle 45, a specially shaped analyzer 6 is used, as indicated by reference numeral B in FIG. Analyzer 6
The components extracted from the optical fiber 1 are guided to the optical receiver 8 through the original fiber 1, and are photoelectrically converted by the optical receiver 8. That is, analyzer 6
The magnitude of the applied magnetic field 5 (if the magnetic field generation source is an electric current, the current) can be determined by electrically measuring the intensity of light emitted from the magnetic field.

[Problem that the invention seeks to solve]

Conventional optical current/magnetic field measurement devices are configured as described above, and require a special shaped and expensive polarizing beam splitter.To avoid this, we recommend using two polarizing beam splitters of the same shape. The problem with this is that the detection sensitivity drops to the lowest level. Furthermore, in order to increase the detection sensitivity of the measurement, the length of the magneto-optical element must be increased, resulting in problems such as an increase in the size of the optical current/magnetic field measuring device.

This invention was made to solve the above-mentioned problems, and aims to simplify the structure of the optical components used, and to obtain an inexpensive, highly sensitive, and compact optical current/magnetic field measuring device. shall be.

[Means for solving problems]

The charging current/magnetic field measuring device according to the present invention is an optically applied current/magnetic measuring device using the Faraday effect, in which a part or all of the light transmitting part of the magneto-optical element is made of a material having natural optical rotation, and the same structure is used. The polarizer 2 and the analyzer are used, and the magneto-optical element is provided with a reflecting means that reflects and bends the light transmitted through the magneto-optical element and causes it to pass back and forth in a direction perpendicular to the direction of the magnetic field to be measured. It is.

[Function] The magneto-optical element of the present invention has natural optical rotation in addition to the Faraday effect, in part or in whole, so even if the polarizer and analyzer are manufactured using a polarizing beam splitter with the same structure, one The angle of the polarization plane shifts and the detection sensitivity increases. Moreover, the reflecting means in each invention does not reflect and bend the transmitted light within the magneto-optical element, but allows it to pass back and forth in a direction perpendicular to the applied magnetic field. It has a long length and has the same effect as the Shinen, but it is small and has high sensitivity.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, and in FIG. 1, the same reference numerals indicate the same groove configurations as in the conventional example. 1 is a light source, 2 is an output fiber, 5 is a magnetic field to be measured, T is an original fiber, and 8 is an original receiver. 3g is a polarizer, 3b is an analyzer, and the polarizer 3a and analyzer 3b have the same structure. The polarizer 3a and the analyzer are arranged so that the original vibration plane (polarization plane) of the linearly polarized light by the polarizer 3a and the vibration plane (polarization plane) of the polarized light detected by the analyzer 3b are perpendicular or parallel to each other. 3b is placed. The arrangement of the polarizer 3a3 and the analyzer 3b is determined depending on whether the natural optical rotation of the magneto-optical element 9, which will be described later, is dextrorotatory or levorotatory. 9 is a magneto-optical element having a Faraday effect and natural optical rotation, and has a pair of substantially parallel total reflection surfaces 9a and 9b that are substantially orthogonal to the magnetic field 5 and formed by a difference in refractive index with the outside; One end surface 9c of the element 9 is substantially perpendicular to the total reflection surfaces 9a and 9b. Further, the other end of the magneto-optical element 9 is a total reflection surface 9
aj? and 9b, respectively, forming an angle of approximately 135.
d2 and an exit surface 9e. Reference numeral 10 denotes a multilayer reflective layer provided in close contact with the end surface 9c, which has one-dimensional reflective properties, and is configured so that the light reflected from each layer interferes and strengthens each other. In addition.

The polarizer 3a is arranged between the output end of the original fiber 2 and the input surface 9d, and the analyzer 3b is arranged between the output surface 9e and the input end of the optical fiber I. Further, the magnetic field 5 is applied so as to pass through the entire magneto-optical element 9. Furthermore, the length L of the magneto-optical element 9 in the direction of the magnetic field 5 is adjusted to such a width that the polarization plane of the linearly polarized light incident on the magneto-optical element 9 rotates 45 times due to natural optical rotation upon exiting the magneto-optical element 9. There is. In this way, 1. Normally, in order to maximize the detection sensitivity, when there is no natural rotation, the i-photon 3a and the analyzer 3b are arranged so that their polarization planes form an angle of 4f. Natural rotation angle ±45 (however.

The sign depends on the direction of the chest. ), the polarizer 3a2 and the analyzer 3b can be used with the same structure as long as they are arranged as described above.

Next, the operation of this embodiment will be explained.

The light that has been linearly polarized by the polarizer 3a enters the incident surface 9d, enters the total reflection surfaces 9a and 9b at an angle greater than the critical angle, and is subjected to multiple total reflections alternately on the total reflection surfaces 9a and 9b. Proceed while doing so. After this progress, this source is reflected by the multilayer reflective film 1o and turned back, and again returns to the direction perpendicular to the magnetic field 5 while being subjected to multiple total reflections alternately on the total reflection surfaces 9a and 9b, and exits from the output surface 9e. Emits light.

The plane of polarization of this emitted linearly polarized light is rotated in accordance with the strength of the magnetic field 5 and the length of the optical path component along the magnetic field 5 due to natural optical rotation p and the Faraday effect. Nine intensities are extracted by the analyzer 3b according to the amount of rotation due to the Faraday effect, guided to the source receiver 8 by the source fiber 7, and photoelectrically converted.

The length of the magneto-optical element 9 in the direction of the applied magnetic field 5 is L, the Werde constant is Ve, and the applied magnetic field 5 is H, and light travels back and forth (n+'') inside the magneto-optical element 9 along the applied magnetic field 5. To be sure, the rotation angle θ of the polarization plane of linearly polarized light due to the Faraday effect is θ=(2n+1)·L−ve−H (where n is a positive number).

The length of the optical path component in the magneto-optical element 9 along the applied magnetic field 5 of the light is (2n+1)·L, and the rotation angle of the polarization plane is (2n+1) times that of the conventional case where the light is not subjected to multiple reflections. , the measurement sensitivity of current and magnetic field increases accordingly.

The linearly polarized light transmitted through the magneto-optical element 9 has its plane of polarization rotated by an angle of 4i10, which is the rotation angle θ due to the Faraday effect and the optical rotation angle 45 due to natural optical rotation. The applied magnetic field 5 (if the source of the magnetic field is a current, the current) can be measured by being guided to the original receiver 8 and subjected to photoelectric conversion.

FIG. 2 shows another embodiment of the present invention.
Same code 1.2, 3a, 3b, 5.7~10°9a~9e
indicates the same configuration as that shown in FIG. This embodiment differs from the embodiment shown in FIG. 1 in that multilayer reflective films 11 and 12 are provided in close contact with total reflection surfaces 9a and 9b, which are boundary surfaces, respectively. The multilayer reflective films 11 and 12 have the same characteristics as the multilayer reflective film 10.

The multilayer reflective films 10 to 12 may be the same multilayer reflective film. In this embodiment, the element within the magneto-optical element 9 is multiple-reflected by the multilayer reflective films 112 and 12 and reciprocates within the magneto-optical element 9 in a direction perpendicular to the direction of the magnetic field 5. In this embodiment as well, the polarizer 3a2 and analyzer 3b having the same configuration can be used based on the same principle as in the above embodiment, and the measurement sensitivity is increased. In this example,
Since there is no need to consider the critical angle conditions of the interfaces 9a2 and 9b, there is no need to take the refractive index of the magneto-optical element 9 into consideration, and the degree of freedom in selecting the magneto-optical element 9 is greatly expanded.

In each of the above embodiments, the entire magneto-optical element has been described as having natural optical rotation, but a part of the magneto-optical element may have natural optical rotation. Even in this case,
The dimensions of the magneto-optical element are limited so that the plane of polarization rotates by an angle of 45 degrees due to natural optical rotation.

〔Effect of the invention〕

As described above, according to the present invention, part or all of the magneto-optical element of the optical current/magnetic field measuring device is replaced with a material having natural optical rotation, and the plane of polarization of linearly polarized light is rotated by the required angle. By multiple-reflecting linearly polarized light within the magneto-optical element, the rotation angle due to the Faraday effect is increased, so even if a polarizing beam splitter with the same shape is used as a polarizer and analyzer, high sensitivity can be achieved. The optical components have a simple structure, are inexpensive, and have the advantage of being compact and highly sensitive.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an optical current/magnetic field measuring device according to one embodiment of the present invention, FIG. 2 is a block diagram showing an optical current/magnetic field measuring device according to another embodiment of the present invention, and FIG. Figures 4 and 4 are configuration diagrams showing a conventional party name current/magnetic field measuring device. In the figure, 1 is the light source, and 2 and 7 are the original fibers. 3a is a polarizer, 3b is an analyzer, 5 is an applied magnetic field, 8 is an original receiver, 9 is a magneto-optical element, and 10 to 12 are multilayer reflective films. In addition, in FIG. 1, the same reference numerals indicate the same or equivalent parts. Patent applicant Mitsubishi Electric Corporation (2 others) - m - 0 knots - ÷

Claims (4)

[Claims] (1) It has a magneto-optical element having a Faraday effect and to which a magnetic field to be measured is applied, and a polarizer and an analyzer disposed on the magneto-optic element, and the light passes through the magneto-optical element from the polarizer. In an optical current/magnetic field measuring device that measures the magnitude of current and magnetic field by photoelectrically converting the light obtained through the analyzer, when light passes through the magneto-optical element, The magneto-optical element is provided with a reflecting means that reflects and bends the light while reciprocating and transmitting the light in a direction perpendicular to the direction of the magnetic field to be measured, and at least a part of the light transmitting part of the magneto-optical element has natural optical rotation. An optical current/magnetic field measurement device characterized in that the polarizer and the analyzer have the same structure by utilizing the natural optical rotation due to the natural optical rotation. (2) The reflecting means includes a pair of substantially parallel total reflection surfaces to the outside of the magneto-optical element in a direction substantially perpendicular to the direction of the magnetic field to be measured, and the magneto-optical device substantially perpendicular to the total reflection surfaces. 2. The optical current/magnetic field measuring device according to claim 1, characterized in that the device comprises a multilayer reflective film formed in close contact with one end surface of the device. (3) The reflecting means is arranged on a pair of substantially parallel boundary surfaces of the magneto-optical element in a direction substantially perpendicular to the direction of the magnetic field to be measured, and on one end surface of the magneto-optical element that is substantially perpendicular to the boundary surface. 2. The optical current/magnetic field measuring device according to claim 1, comprising a multilayer reflective film formed in close contact with each other. (4) The length of the optical path of the portion of the magneto-optical element having natural optical rotation is adjusted so that the plane of polarization of the linearly polarized light is rotated by 45° when the linearly polarized light passes through the optical path. An optical current/magnetic field measuring device according to any one of claims 1 to 3.